Former Turing Pharmaceuticals CEO Martin Shrkeli has refused to comply with a subpoena to testify in front of a Senate panel, which convenes next week to discuss drug prices, ArsTechnica reports.

It's likely Shkreli also won't appear before a House committee investigation, given his disdain for the separate subpoena. Shkreli took to Twitter to discuss the notice, writing, "Found this letter. Looks important."

Shrkeli stepped down as Turing CEO following his December fraud arrest for using a public company's assets to cover his debts.